Electrochemical dimerization of N,N'-diphenylbenzidine (DFB) has been studied in a water/DMF (20/80, v/v) mixture by cyclic voltammetry and controlled potential techniques. The data obtained show that anodically generated N-4,N-4'-diphenyl-[1,1'-bi(cyclohexylidene)]-2,2',5,5'-tetraene-4,4'-diimine (DFBox) reacts with the parent molecule to form a dimer of DFB. The efficient electrochemical synthesis of DFB dimer was successfully carried out under constant current conditions in an undivided cell using carbon anode and stainless steel cathode in water/DMF (20/80, v/v) mixture. The voltammetric and computational data show that the oxidation of dimer is easier than that of monomer (DFB). (C) 2019 The Electrochemical Society.